我的代码java.lang.NullPointerException中有错误：'；布尔值java.lang.String.equals（java.lang.Object）'；关于空对象引用

这是我的错误代码

private void readMessage() {
        chatList = new ArrayList<>();
        DatabaseReference dbRef = FirebaseDatabase.getInstance().getReference("Chats");
        dbRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                chatList.clear();
                for (DataSnapshot ds: snapshot.getChildren()){
                    ModelChat chat = ds.getValue(ModelChat.class);
                    if (chat.getReceiver().equals(myUid) && chat.getSender().equals(hisUid) ||
                            chat.getReceiver().equals(hisUid) && chat.getSender().equals(myUid)){
                        chatList.add(chat);
                    }

                    //adapter
                    adapterChat = new AdapterChat(ChatActivity.this, chatList, hisImage);
                    adapterChat.notifyDataSetChanged();
                    //set adapter to recylerview
                    recyclerView.setAdapter(adapterChat);
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {

            }
        });
    }

这是AdapterChat.java

public class AdapterChat extends RecyclerView.Adapter<AdapterChat.MyHolder>{

    private static final int MSG_TYPE_LEFT = 0;
    private static final int MSG_TYPE_RIGHT = 1;
    Context context;
    List<ModelChat> chatList;
    String imageUrl;

    FirebaseUser fUser;

    public AdapterChat(Context context, List<ModelChat> chatList, String imageUrl) {
        this.context = context;
        this.chatList = chatList;
        this.imageUrl = imageUrl;
    }

    @NonNull
    @Override
    public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        //inflate layout: row_chat_left.xml for receiver, row_chat_right.xml for sender
        if (viewType == MSG_TYPE_RIGHT){
            View view = LayoutInflater.from(context).inflate(R.layout.row_chat_right, parent, false);
            return new MyHolder(view);
        }
        else {
            View view = LayoutInflater.from(context).inflate(R.layout.row_chat_left, parent, false);
            return new MyHolder(view);
        }
    }

    @Override
    public void onBindViewHolder(@NonNull MyHolder holder, int position) {
        //get data
        String message = chatList.get(position).getMessage();
        String timeStamp = chatList.get(position).getTimestamp();

        //convert timestamp to dd/mm/yyyy hh:mm am/pm
        Calendar calendar = Calendar.getInstance(Locale.ENGLISH);
        calendar.setTimeInMillis(Long.parseLong(timeStamp));
        String dateTime = DateFormat.format("dd/MM/yyyy hh:mm aa", calendar).toString();

        //set data
        holder.messageTv.setText(message);
        holder.timeTv.setText(dateTime);
        try {
            Picasso.get().load(imageUrl).into(holder.profileIv);
        }
        catch (Exception e){

        }

        //set seen/delivered status of message
        if (position ==  chatList.size()-1){
            if (chatList.get(position).isSeen()){
                holder.isSeenTv.setText("Seen");
            }
            else {
                holder.isSeenTv.setText("Delivered");
            }
        }
        else {
            holder.isSeenTv.setVisibility(View.GONE);
        }
    }

    @Override
    public int getItemCount() {
        return chatList.size();
    }

    @Override
    public int getItemViewType(int position) {
        //get currently signed in user
        fUser = FirebaseAuth.getInstance().getCurrentUser();
        if (chatList.get(position).getSender().equals(fUser.getUid())){
            return MSG_TYPE_RIGHT;
        }
        else {
            return MSG_TYPE_LEFT;
        }
    }

    //view holder class
    class MyHolder extends RecyclerView.ViewHolder{

        //views
        ImageView profileIv;
        TextView messageTv, timeTv, isSeenTv;

        public MyHolder(@NonNull View itemView) {
            super(itemView);

            //init views
            profileIv = itemView.findViewById(R.id.profile_IV_chat_left);
            messageTv = itemView.findViewById(R.id.message_Tv);
            timeTv = itemView.findViewById(R.id.time_Tv);
            isSeenTv = itemView.findViewById(R.id.is_Seen_Tv);
        }
    }

}

---

谢谢

您的myUid未设置值。方法checkUserStatus在onStart（）中调用，但readMessage（）在onCreate（）中调用。Lyfecycle活动omCreate（）->onStart（）->onResume（）等。在调用readMessage（）之前，需要在onCreate（）中使用init变量

例如：

checkUserStatus();
readMessage();

---

请发布完整的错误报告。很难说NPE发生在什么地方。请在代码中提到出现异常的那一行。

public class AdapterChat extends RecyclerView.Adapter<AdapterChat.MyHolder>{

    private static final int MSG_TYPE_LEFT = 0;
    private static final int MSG_TYPE_RIGHT = 1;
    Context context;
    List<ModelChat> chatList;
    String imageUrl;

    FirebaseUser fUser;

    public AdapterChat(Context context, List<ModelChat> chatList, String imageUrl) {
        this.context = context;
        this.chatList = chatList;
        this.imageUrl = imageUrl;
    }

    @NonNull
    @Override
    public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        //inflate layout: row_chat_left.xml for receiver, row_chat_right.xml for sender
        if (viewType == MSG_TYPE_RIGHT){
            View view = LayoutInflater.from(context).inflate(R.layout.row_chat_right, parent, false);
            return new MyHolder(view);
        }
        else {
            View view = LayoutInflater.from(context).inflate(R.layout.row_chat_left, parent, false);
            return new MyHolder(view);
        }
    }

    @Override
    public void onBindViewHolder(@NonNull MyHolder holder, int position) {
        //get data
        String message = chatList.get(position).getMessage();
        String timeStamp = chatList.get(position).getTimestamp();

        //convert timestamp to dd/mm/yyyy hh:mm am/pm
        Calendar calendar = Calendar.getInstance(Locale.ENGLISH);
        calendar.setTimeInMillis(Long.parseLong(timeStamp));
        String dateTime = DateFormat.format("dd/MM/yyyy hh:mm aa", calendar).toString();

        //set data
        holder.messageTv.setText(message);
        holder.timeTv.setText(dateTime);
        try {
            Picasso.get().load(imageUrl).into(holder.profileIv);
        }
        catch (Exception e){

        }

        //set seen/delivered status of message
        if (position ==  chatList.size()-1){
            if (chatList.get(position).isSeen()){
                holder.isSeenTv.setText("Seen");
            }
            else {
                holder.isSeenTv.setText("Delivered");
            }
        }
        else {
            holder.isSeenTv.setVisibility(View.GONE);
        }
    }

    @Override
    public int getItemCount() {
        return chatList.size();
    }

    @Override
    public int getItemViewType(int position) {
        //get currently signed in user
        fUser = FirebaseAuth.getInstance().getCurrentUser();
        if (chatList.get(position).getSender().equals(fUser.getUid())){
            return MSG_TYPE_RIGHT;
        }
        else {
            return MSG_TYPE_LEFT;
        }
    }

    //view holder class
    class MyHolder extends RecyclerView.ViewHolder{

        //views
        ImageView profileIv;
        TextView messageTv, timeTv, isSeenTv;

        public MyHolder(@NonNull View itemView) {
            super(itemView);

            //init views
            profileIv = itemView.findViewById(R.id.profile_IV_chat_left);
            messageTv = itemView.findViewById(R.id.message_Tv);
            timeTv = itemView.findViewById(R.id.time_Tv);
            isSeenTv = itemView.findViewById(R.id.is_Seen_Tv);
        }
    }

}

if (chat.getReceiver().equals(myUid) && chat.getSender().equals(hisUid) ||
chat.getReceiver().equals(hisUid) && chat.getSender().equals(myUid)){
chatList.add(chat);

checkUserStatus();
readMessage();